SPI MOSI slow rise

Bojun Pan

Other Parts Discussed in Thread: TMS570LS0332

Hi,

We are connecting the Hercules SPI2 to CP2120 SPI/I2C chip. We find a slow rise problem on Hercules MOSI line(CP2120 MISO line).

The green line below is the MOSI line from Hercules(CP2120 MISO line).

The odd part is that MISO line looks okay and it runs to the same locations.

Any idea why that happens?

Thanks for your help!

Bojun

over 9 years ago

0 Bob Crosby over 9 years ago

TI__Guru 72500 points

Which Hercules device are you using and what are the pin connections between the micro and the CP2120? Is there a resistor between the SIMO pin on the micro and the MOSI pin of the CP2120? (If so, double check the resistance value.)

0 Bojun Pan over 9 years ago in reply to Bob Crosby

Prodigy 130 points

Hi Bob,

Thanks for your reply.

TMS570LS0332PZ is the one we use.

No, there is no resistor in between.

Thanks.

Bojun

0 Bob Crosby over 9 years ago in reply to Bojun Pan

TI__Guru 72500 points

Are you using MibSPI1, SPI2 or SPI3?

0 Bojun Pan over 9 years ago in reply to Bob Crosby

Prodigy 130 points

We are using SPI2.

0 Bob Crosby over 9 years ago in reply to Bojun Pan

TI__Guru 72500 points

Then, just to verify, you have pin 70 of the TMS570LS0332PZ connected directly to pin 19 of the CP2120?

0 Bojun Pan over 9 years ago in reply to Bob Crosby

Prodigy 130 points

Hi Bob,

Actually our problem is on pin 69.

But anyway, both pin 69 and pin 70 are directly connected to CP2120.

Thanks.

Best Regards,
Bojun Pan

0 Bob Crosby over 9 years ago in reply to Bojun Pan

TI__Guru 72500 points

You need to use the TMS570LS0332 as the master since the CP2120 is only a slave. In master mode, pin 69 is an input. It should be connected to CP2120 pin 20, which is an output.

0 Bojun Pan over 9 years ago in reply to Bob Crosby

Prodigy 130 points

Yes, TMS570LS0332 pin 69 is connected to CP2120 Pin 20. pin 70 is connected to pin 19.

0 Bob Crosby over 9 years ago in reply to Bojun Pan

TI__Guru 72500 points

So the slow rise time you see is on the micro's pin 69 which is tied to the CP2120's pin 20. This is MISO, not MOSI. The issue then is in the CP2120, as it is responsible for driving this line. Is it possible that there is a bad solder joint on pin 20 of the CP2120?

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SPI MOSI slow rise